Burner tip having an air channel structure and a fuel channel structure for a burner, and method for producing said burner tip

ABSTRACT

A burner tip for installation in a burner, wherein the burner tip has a surface facing a combustion chamber, an air channel structure leading to the surface and defining an air channel, and a fuel channel structure leading to the surface, and wherein the fuel channel structure defines a fuel channel, which extends in a surface region of the burner tip in a first direction parallel to the surface and then extends back, at least in part, in a second direction, different from the first direction, in order to cool the surface region of the burner tip by a fuel flowing through the fuel channel during operation of the burner tip.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is the US National Stage of International Application No. PCT/EP2018/050206 filed Jan. 4, 2018, and claims the benefit thereof. The International Application claims the benefit of German Application No. DE 10 2017 200 643.9 filed Jan. 17, 2017. All of the applications are incorporated by reference herein in their entirety.

FIELD OF INVENTION

The present invention relates to a burner tip having an air channel structure and a fuel channel structure, in particular for a burner in a gas turbine. Furthermore, a method, in particular an additive method, for manufacturing the burner tip is described.

The burner tip may be provided for use in a flow machine, in particular in the hot gas path of a gas turbine. The component furthermore advantageously comprises a nickel-base alloy and/or superalloy, in particular a nickel- or cobalt-based superalloy. The alloy may be precipitation-hardened or precipitation-hardenable.

BACKGROUND OF INVENTION

Burner tips of the kind indicated above are known from EP 2 196 733 A1, for example. The burner tip described there can be used in a gas turbine, for example, wherein the burner tip forms the downstream end of a burner lance which is arranged in a main channel for combustion air. The burner tip has a double-walled design, wherein the outer wall creates a heat shield which is intended to keep the combustion heat generated away from the inner wall. An annular cavity, in other words an annular space, is therefore arranged between the outer wall and the inner wall, which cavity can have air flowing through it via openings for cooling purposes. In the embodiment described, the heat shield must be designed to withstand the heat stress caused by the combustion taking place in the downstream combustion chamber. The outer wall of the burner tip therefore represents the limiting factor for the service life of the burner tip.

SUMMARY OF INVENTION

The problem addressed by the invention is that of developing a burner tip of the kind specified above in such a manner that an improvement in the service life of the component results. In particular, the present invention should facilitate improved cooling of the burner tip. Furthermore, the problem addressed by the invention is that of specifying a method for manufacturing a burner tip of this kind.

The manufacture may, for example, take place by lost-core casting. According to a solution to the problem specified above, it is however particularly advantageous for an additive manufacturing method to be used for manufacturing. In this case, the burner tip may advantageously be produced in one piece and with a particularly complex and/or optimized design in relation to the cooling effect, wherein additive manufacturing in particular allows geometrically complex structures with an advantageously large surface for heat transfer.

An additive manufacturing method within the meaning of this application should be understood to refer to a method in which the material from which a component is to be produced is added to the component during its development. This means that the component is developed in its final form or at least in a form approximating to this. The construction material or primary material is advantageously in powder form, wherein the additive manufacturing process means that the material used to manufacture the component is physically consolidated by applying energy.

So that the component can be manufactured, the data describing said component (CAD model) is prepared for the chosen additive manufacturing process. In order to generate instructions for the production plant, the data is converted into component data adapted to the manufacturing process, so that suitable process stages for successive manufacturing of the component can be followed in the production plant. The data is prepared for this in such a manner that the geometric data for the layers (slices) of the component to be manufactured in each case are supplied, this also being referred to as slicing.

Selective laser sintering (or SLS), selective laser melting (or SLM), electron beam melting (or EBM), laser metal deposition (or LMD) or gas dynamic cold spray (or GDCS) can be given as examples of additive manufacturing. These methods are particularly suitable for the processing of metallic materials in the form of powders, with which structural components can be manufactured.

In the case of SLM, SLS and EBM, the components are manufactured layer-by-layer in a powder bed. These methods are therefore also referred to as powder bed-based additive manufacturing methods. A layer of powder is produced in the powder bed in each case, which layer is then melted or sintered locally by the energy source (laser or electron beam) in those areas in which the component is to be created. The component is therefore produced by successive layers and can be removed from the powder bed following completion.

In the case of LMD and GDCS, the powder particles are supplied straight to the surface on which material is to be deposited. In the case of LMD, the powder particles are melted by a laser right at the target point on the surface and thereby create a slice of the component being manufactured. In the case of GDCS, the powder particles are greatly accelerated so that they remain adhering to the surface of the component, primarily on account of their kinetic energy, with simultaneous deformation.

GDCS and SLS have in common the feature that the powder particles are not completely melted during these processes. This also facilitates, among other things, the manufacture of porous structures when gaps between the particles are retained. In the case of GDCS, melting takes place in the peripheral area of the powder particles at most, said powder particles being able to melt on account of the severe deformation of their surface. In the case of SLS, when selecting the sintering temperature it is important to ensure that it lies below the melting temperature of the powder particles. On the other hand, in the case of SLM, EBM and LMD, the energy application is deliberately high enough for the powder particles to be completely melted.

The problem referred to above is solved by the subject matter of the independent patent claims. Advantageous embodiments are the subject matter of the dependent patent claims.

One aspect of the present invention relates to a burner tip for installation in a burner, wherein the burner tip has a surface facing a combustion chamber and an air channel structure leading to the surface and defining an air channel and also a fuel channel structure leading to the surface. The fuel channel structure defines a fuel channel which runs in a surface region of the burner tip in a first direction parallel to the surface and then extends back or is curved or deflected, at least in part, in a second direction, different from the first direction, in order to cool the surface region of the burner tip by a fuel flowing through the fuel channel when the burner tip is in operation.

The “backwards extension” or curved course of the fuel channel means that—during operation of the burner tip, for example during use of a gas turbine—a cooling action can advantageously take place in a particularly effective manner in the surface region of the burner tip through the fuel. This means that the consumption of compressor air which is valuable to the efficiency of a flow machine is no longer relied upon when cooling the surface or the surface region of the burner tip. In addition, feed systems for this compressor air can be saved and the corresponding components advantageously simplified.

In one embodiment, the fuel channel runs with multiple turns parallel to the surface and in the surface region. In other words, the fuel channel is advantageously diverted multiple times parallel to the surface or extends according to the diversion.

In one embodiment, the fuel channel runs at least in part along an axis of symmetry of the burner tip or a main flow direction during operation of the same.

In one embodiment, the fuel channel extends starting from its course along the first direction into an inside of the burner tip. According to this embodiment, a region of the surface (surface region) spaced apart from the surface may also be advantageously cooled during operation of the burner tip. This in turn advantageously affects the service life of the structural component as a whole.

In one embodiment the first direction encloses an angle of between 160° and 200°, advantageously of 180°, relative to the second direction. This embodiment allows a particularly effective recirculation or diversion of the fuel channel, as described above.

The term “surface region” advantageously describes a structural region of the burner tip proximate to the aforementioned surface.

In one embodiment, the fuel channel opens out subsequently, i.e. following its diversion into the inside of the burner tip, via at least one further directional change, for example a deflection of between 70° and 110°, into the surface. This embodiment enables efficient cooling when the burner tip is in use and, at the same time, an advantageous design of the burner tip to be realized, since efficient cooling by the fuel when the burner tip is in use and, at the same time, preheating of the fuel correspondingly to be fed into the combustion chamber are made possible.

In one embodiment, the fuel channel subsequent to its course along the first direction and, advantageously, before an opening into the surface, has a region with an enlarged cross section, in particular an interaction or collecting space. According to this embodiment, a heat transfer from a surface region to a fuel which is located in the collecting space when the burner tip is in operation, or flows through said collecting space, can be particularly advantageously facilitated. In particular, the enlarged cross section means that an enlarged volume is available for interaction and for the heat transfer described, as a result of which a thermal capacity (for absorbing the heat acting on the surface during operation of the burner tip) can be effectively increased.

In one embodiment, the air channel structure comprises a central air channel which leads to a central outlet opening in the burner tip. In particular, the air channel structure may represent or define the aforementioned central air channel.

In one embodiment, the burner tip has an inlet region. Both the air channel and the fuel channel advantageously run coaxially in the inlet region. In other words, the air channel structure and the fuel channel structure are correspondingly designed.

In one embodiment, the fuel channel runs in the inlet region radially outside the air channel. In other words, the fuel channel structure and the air channel structure may be configured accordingly.

In one embodiment, the burner tip has an outlet region which is advantageously arranged offset (axially) along an axis of symmetry. The outlet region from which both an air flow and also a fuel flow can advantageously emerge advantageously comprises the surface described or the surface region.

In one embodiment, the fuel channel runs in the outlet region at least partly radially within the air channel.

In one embodiment, the fuel channel and the air channel run in an interlocking or entwined manner or are interwoven with one another, so that the surface region of the burner tip can be advantageously cooled in addition by an air flow—and not exclusively by a fuel flow. The fuel channel and air channel advantageously run without fluidic communication with one another, however. Alternatively, the air channel and fuel channel may be fluidically connected to one another at least in part.

In one embodiment, the burner tip is at least largely designed to be rotationally symmetrical about the axis of symmetry described.

In one embodiment, the air channel and/or the fuel channel run at least partly along a circumferential direction or a tangential direction of the burner tip.

In one embodiment, advantageously in the outlet region, the fuel channel structure has vanes which subdivide the fuel channel—at least sectionally—into a plurality of sub-channels. In this way, a cooling action while the burner tip is operating can likewise advantageously be optimized by an improved heat transfer. The aforementioned vanes—just like other parts of the fuel channel structure or the burner tip—may exhibit any forms which can be achieved under certain circumstances exclusively by additive manufacturing technology.

In one embodiment, the fuel channel structure in the inlet region forms an annular chamber.

In one embodiment, the fuel channel structure is formed in such a manner that the fuel channel runs through the annular chamber following its course in the second direction and before it opens out into the surface.

In one embodiment, the fuel channel structure in the outlet region has a plurality of fuel channels which lead via the surface into the combustion chamber or open out into the aforementioned surface. Through this embodiment, an improved and/or more homogeneous cooling of the surface can be advantageously achieved.

In one embodiment, the air channel runs at least in part through the fuel channel, or vice versa. This embodiment enables a particularly compact and effective design of the burner tip to be achieved.

In one embodiment, the air channel structure has a plurality of air channels which open out in the surface at different outlet angles relative to the surface or a surface normal, for example, or lead into the combustion chamber. Through this embodiment, an efficient surface cooling or film cooling of the surface can be achieved particularly advantageously.

In one embodiment, the air channel structure and/or the fuel channel structure define channel cross sections which have a cross-sectional shape that differs from a round, in particular circular, shape, for example an elliptical or star-shaped cross section. Through this embodiment, a heat transfer from the surface to a fuel or to an air flow can advantageously be furthermore improved and/or optimized during operation of the burner tip by a cross-sectional area that is enlarged by comparison with a circular cross section.

In one embodiment, the surface is formed by an openly porous wall or wall structure of the burner tip which, through its porosity, defines a plurality of air channels. According to this embodiment, the surface region can therefore be flowed through by cooling air particularly homogeneously, for example, in order to bring about effective cooling in the region of the burner tip.

In one embodiment, the burner tip is manufactured additively or by an additive manufacturing process.

In one embodiment, the burner tip is produced integrally or in one piece.

A further aspect of the present invention relates to a flow machine, for example a gas turbine, comprising the burner tip described.

A further aspect of the present invention relates to a method for manufacturing the burner tip, wherein the burner tip is manufactured or can be manufactured, in particular, additively and/or integrally.

Configurations, features and/or advantages which relate to the burner tip or the flow machine in the present case may, in addition, relate to the method or vice versa.

BRIEF DESCRIPTION OF THE DRAWINGS

Further details of the invention are described below with the help of the figures.

FIG. 1 shows a schematic sectional view of a burner in which an exemplary embodiment of the burner tip according to the invention is fitted.

FIG. 2 shows a schematic sectional view of a burner tip in an embodiment according to the invention.

FIG. 3 shows a schematic sectional view of part of the burner tip according to an inventive embodiment.

FIG. 4 shows a schematic sectional view of a burner tip in a further inventive embodiment.

FIG. 5 shows a schematic sectional view of part of the burner tip according to a further inventive embodiment.

FIG. 6 shows an exemplary embodiment of the method according to the invention in a schematic sectional view.

DETAILED DESCRIPTION OF INVENTION

In the exemplary embodiments and figures, identical elements or those having the same effect are each provided with the same reference numbers. The elements shown and the proportions thereof should not in principle be regarded as being to scale; instead, individual elements may be depicted for improved illustration and/or for better understanding as disproportionately thick or large.

A burner 11 is depicted in FIG. 1 which has a jacket 12 in which a main channel 13 for air is formed. The jacket 12 is symmetrically constructed about a longitudinal axis and/or an axis of symmetry 14 and has a burner lance 15 in the center of the main channel 13. The burner lance 15 is fixed in the main channel 13 with webs 16. Moreover, guide vanes 17 extend between the burner lance 15 and the jacket 12 which cause the air to spin about the axis of symmetry 14, as can be inferred from the air arrows 18 indicated.

The burner lance 15 has a burner tip 19 at the downstream end, wherein said burner tip is supplied with air via a central air channel 20 and with fuel 23 via an annular channel 22 arranged about the air channel 20.

The fuel 23 may be in gas or liquid form. The fuel may, in particular, be natural gas, gas or fluid containing hydrogen or another fuel.

The air (cf. air flow or air channel 20) and the fuel 23 are expelled via openings in the burner tip, which are not depicted in greater detail, and thereby mixed with the air flow from the main channel 13. The air 21 customarily cools the burner tip 19 during this process (see below). The burner 11 adheres to the functional principle of a pilot burner. Said burner may, for example, be fitted in a combustion chamber BR, for example of a gas turbine, wherein the combustion chamber BR in this case creates a surrounding area 30 of the burner tip 19.

FIG. 2 shows a schematic sectional view of a burner tip 19, as described above. In particular, a section along the axis of symmetry 14 is depicted. The axis of symmetry 14 may likewise denote a rotational symmetry of the burner tip 19.

The burner tip 19 has an inlet region EB. Furthermore, the burner tip 19 has an outlet region AB. The outlet region AB is attached to the inlet region EB along the axis of symmetry 14 or is arranged axially offset with respect to the inlet region EB.

What can furthermore be seen in FIG. 2 is the central air channel 20 running along the axis of symmetry 14. The air channel 20 leads to an outlet opening 24 of the burner tip 19. A further burner lance can be housed in this air channel during operation (see below). During operation of the burner tip 19, for example when used in a gas turbine, the burner tip 19 in the air channel 20 has air, in particular compressor air, flowing through it, with air entering the air channel 20 in the inlet region EB and leaving said air channel again in the outlet region AB. The air channel 20 is defined by an air channel structure 21.

During operation of the burner tip 19, an air flow in the air channel 20 is indicated by dotted arrows in FIG. 2.

The burner tip 19 furthermore has a fuel channel structure 32. The fuel channel structure 32 defines a fuel channel 33.

During operation of the burner tip 19, a fuel flow in the fuel channel 33 is indicated by the solid arrows in FIG. 2.

The fuel channel 33 is arranged radially outside the air channel 20, so that when the burner tip 19 is in operation a fuel 23 can be guided radially outside the described air flow (along the air flow direction).

The fuel channel structure 32 may comprise or define an outer wall 28 of the burner tip 19.

The fuel channel structure 21 may comprise or define an inner wall 29 of the burner tip 19.

The burner tip 19 or the air channel structure 21 is advantageously configured in such a manner that the air channel 20 tapers from the inlet region EB into the outlet region AB. Subsequent to a corresponding conical or tapering course, the air channel structure 21 defines the air channel 20 parallel to the axis of symmetry 14 once again.

In the figures, in particular in FIGS. 2 and 4, for ease of reference there are no further components shown in the central air channel 20. When using the burner tip 19, for example during operation of a corresponding gas turbine exhibiting the burner tip (not explicitly identified), further components are advantageously arranged in this central region of the burner tip 19, for example further ignition and/or oil lances. The aforementioned components are crucial to the function of the burner 11 and advantageously simultaneously seal the central air channel in such a manner that an air gap forms which, during operation of the burner tip, causes an effective cooling action of the aforementioned components and/or of the burner tip.

It can furthermore be seen in FIG. 2 that the outer wall is likewise tapered in the outlet region AB or extends to the centrally arranged axis of symmetry 14. In the outlet region AB, the fuel channel structure 32 is configured in such a manner that the fuel channel 33 initially extends parallel to an outer surface OF of the burner tip 19 or runs parallel to the surface OF. In particular, during operation of the burner tip 19, a fuel flow runs along a first direction 1R parallel to the surface OF.

A surface region which has the surface OF is identified using the reference OFB in this present case. In particular, precisely this surface region OFB, advantageously in the outlet region AB of the burner tip 19, should be effectively cooled by a fuel 23 guided through the fuel channel structure 32 during operation of the burner tip 19.

Once the fuel (cf. arrows shown in the fuel channel 33) has run a certain length in the first direction parallel to the surface OF, the fuel channel is diverted by the geometry of the fuel channel structure 32 in a second direction, so that it extends back or is diverted at least in part counter to the first direction and then leaves the surface region OFB of the burner tip 19.

In other words, through the diversion of the fuel channel in the surface region OFB, said region can be efficiently cooled during operation of the burner tip 19 by a fuel, since the fuel is initially conducted close to the surface inside of the component, then diverted, and can later be delivered—possibly conducted through itself—into the combustion chamber BR at a plurality of fuel outlets provided (not explicitly identified in the figures) (cf. FIG. 3 below). Accordingly, the course of the fuel channel 33 or else the geometry of the fuel channel structure 32 may correspond to the design of a so-called “Klein bottle” or resemble this.

The first direction may describe a direction at least partially or in part along the axis of symmetry (in the flow direction) or along a corresponding main flow direction. The second direction advantageously denotes a direction which is different, advantageously precisely opposed, to the first direction. The fuel channel 33 is advantageously diverted from the first direction into the second direction in such a manner that subsequent to its course parallel to the first direction, it initially extends inside the burner tip or the corresponding surface region OFB. In this way, lower structures of the surface region can also be effectively cooled.

The second direction may likewise describe a direction parallel to the surface, but advantageously counter to a main flow direction. The second direction may, alternatively or in addition, be furthermore inclined by 90° or another angle with respect to the first direction.

The burner tip 19 may be configured rotationally symmetrically or approximately rotationally symmetrically relative to its axis of symmetry 14. The second direction may run correspondingly in a circumferential direction of the burner tip 19, for example.

In the circumferential direction (not explicitly identified in the figures) the burner tip 19 may correspondingly exhibit a plurality of fuel channels 33 in the outlet region AB, which fuel channels lead over the surface OF into the combustion chamber BR, in a manner arranged equidistantly and circumferentially for example (cf. FIG. 3 below). The positions of the fuel outlets produced accordingly through the opening-out of the fuel channels 33 in the surface OF may correspond to a conventional design of the fuel tip.

Through the aforementioned diversion or backward extension, for example about an angle between 160 and 220°, advantageously about approx. 180°, a cooling effect of the surface region OFB can be advantageously improved by the fuel which is comparatively cold compared with the compressor air customarily used for cooling. In other words, in order to cool the outer surface of the component, compressed air need no longer necessarily be taken, but instead the far cooler combustion gas (approx. 50° C. rather than 400° C. for conventionally used compressed cooling air from the compressor part of a gas turbine (not explicitly shown)) can be conducted along directly below the component surface for cooling in the surface region OFB.

Subsequent to the backward extension, the fuel channel 33 advantageously experiences a further deflection, for example a deflection between 70 and 110°, so that it can then open out in the surface OF or can leave it in the direction of the combustion chamber BR. In other words, the fuel is retained or collected in the surface region OFB by the geometry of the fuel channel structure 32 for an improved cooling action and can then escape into the combustion chamber BR once again at a given outlet angle and be combusted.

The burner tip 19 described is advantageously produced by an additive manufacturing process, advantageously by selective laser melting (SLM) or electron beam melting (EBM). Additive manufacture, in particular, allows components with integrated functions to be produced. In particular, it is possible for the burner tip 19 described with the complexity of its channel structures, as described, to be manufactured in one piece and without conventionally necessary heat shields by additive means.

Since the burner tip 19 need only conduct a single fluid for cooling purposes, under certain circumstances fewer connections may advantageously be required, as a result of which the manufacture and function of the component can be simplified.

A region B is furthermore shown in FIG. 2, in which region the fuel channel 33 has a larger cross section. This embodiment enables a greater volume of fuel 23 to be advantageously “collected” in the region B, in order to bring about an effective cooling action.

FIG. 3 shows as a detail a cross-sectional view of a burner tip 19, advantageously a section through the surface region OFB (cf. FIG. 2). The outer fuel openings identified by reference number 34 define the shape of the fuel channel 33 (cf. FIG. 2).

The arrows shown in FIG. 3 again indicate the course of the fuel channel 33 or of the fuel 23. In particular, a plurality of fuel channels indicated by the arrows, in particular distributed over a circumference of the burner tip 19, are shown which are advantageously provided but are not visible in FIGS. 2 and 4. In other words, the fuel channel 33 is divided up, advantageously circumferentially, by one or multiple vanes 39 into a plurality of individual fuel sub-channels. This plurality of fuel channels, or else the sub-channels identified using the reference number 34, are advantageously spaced apart from one another circumferentially (by the vanes 39).

The sub-channels 34 are combined—as shown in FIG. 3—running radially inwards, advantageously into a single fuel channel 33 of the fuel tip 19. In this way, during operation of the burner tip 19, a heat transfer from the structure of the burner tip to a fuel flow conducted through the fuel channel 33, and therefore the cooling of the burner tip, can furthermore advantageously be improved.

The geometry of the vanes as described is, in particular, unachievable using conventional manufacturing methods and is therefore manufactured additively and advantageously integrally in accordance with the described teaching, for example by selective laser melting.

By way of example, fuel channels 34 or openings with rectangular cross sections are identified in FIG. 3. Alternatively, however, other cross-sectional shapes can also be used, for example elliptical or star-shaped cross sections, in order to achieve an improved cooling effect due to an enlarged surface and correspondingly improved heat exchange during operation of the burner tip 19.

The fuel channel structure 32 may furthermore form a (complexly formed) annular chamber, in particular in accordance with a rotationally symmetrical embodiment of the burner tip 19 about its axis of symmetry. The fuel channel structure 32 is furthermore advantageously formed in such a manner that the fuel channel 33 runs, subsequent to its course in the second direction 2R and before its opening-out into the surface OF, in the outlet region AB through the annular chamber (cf. the arrows indicating the fuel 23 in FIG. 2).

In particular, the course of the arrows in FIG. 3 represents the diversion of the fuel in the fuel channel 33 due to the geometry of the fuel channel structure 32, in order to be able to effectively cool the surface region OFB of the burner tip 19 during operation of the same.

FIG. 4 shows a sectional representation (longitudinal section) of an alternative embodiment of a burner tip according to the invention. Unlike FIG. 2, the fuel channel 33 runs in the outlet region AB at least partially radially within the air channel 20. Furthermore, the fuel channel 33 and the air channel 20 run at least partially in an interlocking manner, in order to cool the surface region OFB of the burner tip 19 additionally through an air flow, which results in a further improved cooling effect.

The air channel structure 21 has in the inlet region EB openings 25 in the side wall which connect the (central) air channel 20 fluidically to an annular space surrounding the air channel annularly or a plurality of individual air channels.

The aforementioned individual air channels 20 advantageously intersect at least in part the course of the fuel channel structure 33 according to the embodiment of the air channel structure 21.

The aforementioned air channels according to the depiction in FIG. 4 may furthermore lead at different outlet angles, for example outlet angles between 60° and 120° relative to the surface OF or a corresponding surface normal, into the combustion chamber BR. The aforementioned outlet angle of the fuel channels 33 may vary along the axis of symmetry of the burner tip 19, for example. As the outlet angles become smaller (for example smaller than 90°), film cooling on the surface OF of the burner tip 19 may be stronger or weaker.

Furthermore, the air channel structure 21 and the fuel channel structure 32 can define channel cross sections which have a cross-sectional shape that deviates from a round, in particular circular, form. In particular, the aforementioned channel structures may be star-shaped and/or elliptical. All these geometries can be produced using the additive manufacturing method described and therefore allow the inventive advantages of the present invention to be utilized.

In a further embodiment, the surface OF may be formed by an openly porous wall structure (not explicitly identified) which defines a plurality of air channels 20. This geometry may likewise advantageously be realized by additive manufacturing technology and contribute to improved cooling of the burner tip during operation.

FIG. 5 shows—similarly to the representation in FIG. 3—a cross-sectional view of the burner tip (section perpendicular to the axis of symmetry) according to the embodiment of the burner tip described in FIG. 4. Unlike in the representation in FIG. 3, it can be seen in FIG. 5 that additional circular air openings 35 are provided which bring about the cooling effect for the burner tip 19 through air cooling (in addition to the fuel cooling) (cf. FIG. 4). The dotted arrows emerge from the openings 35 and are intended to indicate an air flow, while the solid arrows—similarly to the depiction in FIG. 3—indicate the diversion of the fuel flow according to the present invention.

FIG. 6 depicts in detail how a component 19 according to FIG. 2 or FIG. 4 can be produced by laser melting with a laser beam 37. The detail of a powder bed 36 is depicted in which a part of the air channel structure 21 and/or of the fuel channel structure 32 is manufactured. The fuel channel structure 32 is, for example, similar in design to the depiction in FIG. 2 and advantageously has, among other things, the vanes described above (not shown in FIG. 6) and likewise defines the inventive diversion of the fuel channel.

Following the manufacture of the completed structure, the powder 36 must be removed from the corresponding cavities which form the air channel or the fuel channel system or the corresponding channel structures. This can be achieved by suction, shaking or blowing out, for example.

The invention is not limited to the exemplary embodiments by the description on the basis of said exemplary embodiments, but comprises each novel feature and each combination of features. This includes, in particular, each combination of features in the patent claims, even if this feature or this combination is not itself explicitly indicated in the patent claims or exemplary embodiments. 

1. A burner tip for installation in a burner, comprising: a surface facing a combustion chamber, an air channel structure leading to the surface and defining an air channel, and a fuel channel structure leading to the surface, wherein the fuel channel structure defines a fuel channel which runs in a surface region of the burner tip in a first direction parallel to the surface and then extends back, at least in part, in the surface region in a second direction, different from the first direction, in order to cool the surface region of the burner tip by a fuel flowing through the fuel channel when the burner tip is in operation.
 2. The burner tip as claimed in claim 1, wherein the fuel channel extends starting from its course along the first direction into an inside of the burner tip and then opens out via at least one further directional change into the surface.
 3. The burner tip as claimed in claim 1, wherein the first direction encloses an angle of between 160° and 200° relative to the second direction.
 4. The burner tip as claimed in claim 1, wherein the fuel channel, subsequent to its course along the first direction and before an opening into the surface, has a region with an enlarged cross section.
 5. The burner tip as claimed in claim 1, wherein the air channel structure comprises a central air channel which leads to a central outlet opening in the burner tip.
 6. The burner tip as claimed in claim 1, wherein the burner tip has an inlet region in which both the air channel and the fuel channel run coaxially and an outlet region which is offset with respect to the inlet region along an axis of symmetry.
 7. The burner tip as claimed in claim 6, wherein the fuel channel runs in the inlet region radially outside the air channel.
 8. The burner tip as claimed in claim 6, wherein the fuel channel runs in the outlet region at least partly radially within the air channel.
 9. The burner tip as claimed in claim 1, wherein the fuel channel and the air channel run in an interlocking manner, so that the surface region of the burner tip can be cooled in addition by an air flow.
 10. The burner tip as claimed in claim 1, wherein the fuel channel structure has vanes which subdivide the fuel channel into a plurality of sub-channels.
 11. The burner tip as claimed in claim 6, wherein the fuel channel structure in the inlet region defines an annular chamber and wherein the fuel channel structure is formed in such a manner that the fuel channel runs through the annular chamber subsequent to its course in the second direction and before it opens out into the surface.
 12. The burner tip as claimed in claim 1, wherein the air channel runs at least in part through the fuel channel and wherein the air channel structure has a plurality of air channels which lead into the combustion chamber at different outlet angles relative to the surface.
 13. The burner tip as claimed in claim 1, wherein the air channel structure and the fuel channel structure define channel cross sections which have a cross-sectional shape that differs from a round or circular shape.
 14. The burner tip as claimed in claim 1, wherein the surface is formed by an openly porous wall structure which defines a plurality of air channels.
 15. The burner tip as claimed in claim 1, wherein the burner tip is manufactured additively and integrally.
 16. A gas turbine comprising a burner tip as claimed in claim
 1. 17. A method for manufacturing a burner tip as claimed in claim 1, wherein the burner tip is manufactured additively and integrally.
 18. The burner tip as claimed in claim 2, wherein the fuel channel extends starting from its course along the first direction into an inside of the burner tip and then opens out via at least one further directional change comprising a deflection of between 70° and 110° into the surface. 